<p>Flexibility refers to the ability of a manufacturing system to respond cost effectively and rapidly to changing production needs and requirements. This capability is becoming increasingly important for the design and operation of manufacturing systems, as these systems do operate in highly variable and unpredictable environments.<br /> It is important to system designers and managers to know of different levels of flexibility and / or determine the amount of flexibility required to achieve a certain level of performance. This paper shows several representations schemes for product flexibility and discusses the usefulness and limitations of each.</p>